1. Field of the Invention
The present invention relates to a drive device that is detachably mounted on a lens barrel, a method of controlling the drive device, and a method of adjusting the drive device.
2. Description of the Related Art
Operation rings, such as a focus ring, a zoom ring, and an iris ring, are rotatably provided on the outer periphery of a lens barrel, and the adjustment of an optical system provided in the lens barrel, for example, focusing (focus adjusting), zooming, and iris adjustment are performed by the rotation of these operation rings. The lens barrel is used while being mounted on a camera. However, there are a case in which the operation rings is manually operated (rotated) and a case in which the operation rings are rotated by a drive device, For example, a cameraman who makes a movie tends to prefer manual operation, and a cameraman who takes pictures for television broadcasting prefers the use of a drive device.
Accordingly, a drive device that is detachably mounted on a lens barrel is used to be capable of coping with these use forms. Gradations are formed on the operation rings. Accordingly, when the operation rings are manually operated without using a drive device, the position of each operation ring can be visually checked. However, when a drive device is mounted, it is preferable that the positions of the respective operation rings be detected and be displayed on a camera as a focus distance, a zoom ratio, an aperture value, and the like.
JP2012-42635A discloses a device that optically detects the position of a focus lens in a digital still camera, but does not instruct means for solving particular problems of a drive device that is detachably mounted on a lens barrel. JP2011-107395A and JP2011-107334A relate to a lens barrel on which a drive device is detachably mounted. However, JP2011-107395A merely detects only a specific position of focusing. JP2011-107334A discloses that the present set position of each of a focus lens group, a zoom (variable power) lens group, and an iris provided in a lens barrel are detected by a potentiometer provided in a drive unit (device). The potentiometer generates a voltage corresponding to an angular position thereof. Accordingly, when the drive device is mounted on the barrel, the positioning of the potentiometer and the operation ring needs to be performed by an adjustment tool so that an output voltage of the potentiometer correctly represents the position of the operation ring. For this reason, it is difficult to simply mount the drive device on the lens barrel on site.